Big gas bottles

[Robotstar5]

I think it was Autocare asked how many W size bottles we used at work so here's a pic of our gas "bottles" XXXL size?



I believe we have them filled about once a month.

 

[the snooper]

you dont dont want to use them small disposable things

 

[Robotstar5]

you dont dont want to use them small disposable things

Tried them but filled the local tip in no time with the empties

Did a leak test recently and found we are losing 2 lpm from the system , will be doing a bit of leak detecting during the next shutdown

 

[Luke]

I like how the pipes are nicely frozen up, a day's welding in the garage gets the regulator pretty cold, but I'll never build up that much ice!

 

[Robotstar5]

I like how the pipes are nicely frozen up

Tell me about it, my hands were frozen (even wearing rigger gloves) when I closed the valves for the christmas shutdown

 

[stormin]

Tell me about it, my hands were frozen (even wearing rigger gloves) when I closed the valves for the christmas shutdown

I bet they still hadn't thawed out come New Year with the weather we've had recently.

 

[Welderpaul]

What pressure are the tanks filled to? Same as a normal bottle?

 

[hotrodder]

From the ice they're liquid argon cryogenic tanks aren't they?

 

[Welderpaul]

From the ice they're liquid argon cryogenic tanks aren't they?

Shielding gas the high draw-off rates make ice form on the pipes.

Poor Robotstar having to change those cylinders once a month.

 

[hotrodder]

Place near me had cryogenic argon tanks. Liquid argon drawn off as a gas for welding, tanker comes round to refill the cryo tank rather than exchange cylinders

 

[pedrobedro]

The last foundry I worked at had an oxygen tank 20 feet tall. The Union Carbide tanker used to come from Belgium to refill it and he used to keep everyone in contraband fags and booze

 

[backpurge]

I like how the pipes are nicely frozen up, a day's welding in the garage gets the regulator pretty cold, but I'll never build up that much ice!

The frozen pipes are not really anything to do with draw off rates,it usually has more to do with ambient temperatures/moisture in the atmosphere etc.

The liquid in the vessels is stored at around minus 196 deg C and around 18 bar pressure, as the tank contents is drawn off it is designed to vapourise and turn into gas as it passes through the pipework and vapouriser. It is far more economical for large users to buy and store gas as liquid as opposed to gas, a rough comparrision......whan a cup full of liquid gas vapourises it produces enough gas to fill an average size room (I think the expansion rate is around 670 times but might be wrong)

 

[Luke]

The frozen pipes are not really anything to do with draw off rates

It certainly is, in my situation at home with either compressed air or welding gas cylinders.

The liquid in the vessels is stored at around minus 196 deg C

Why isn't the whole cylinder covered in ice?

and around 18 bar pressure,

18 bar isn't that high?

In my situation, it's definitely the case of an expanding gas requiring energy. that energy is drawn from the surrounding atmosphere as heat, a lack of heat produces a drop in temperature - so eventually it gets cold enough to freeze out the water in the atmosphere.

The best example I have seen personally was when I emptied my 300L air tank through a 1/2" ball valve, from 100 psi to ambient. the valve was pointing at a breeze block wall, 6" away and by the time the tank was empty, there was a 2" icicle projecting from the breeze block.

Same theory behind air tools getting cold as you use them - this is due to the pressure drop/expansion across the tool inlet and exhaust.

 

[superls]

after a heavy welding session with long rins with the mig my regulator starts to freeze up on a large bottle, so id say its everything to do with draw off rates.

 

[eil]

Its to do with the ambient temp and the drop in pressure of the liquid in the tank entering the lower pressure in the pipework, its doing it for about 18 hours per day in your own homes, its called a Refrigerator, except that gas is recovered and put back in the tank.

 

[backpurge]

It certainly is, in my situation at home with either compressed air or welding gas cylinders.

Not the case with cryogenic vessels, remember the temperature differentials involved when dealing with cryogenic liquids, it's a totally different situation than with cylinder gases

Why isn't the whole cylinder covered in ice?

It is actually a vessel within a vessel, like a huge thermos flask with a vacuum and super insulating material such as Perlite between the two vessels to reduce temperature tracking, if you get a build up of frost or ice on the actual vessel you've got big problems

18 bar isn't that high?

You will only need above 18 bar if your end application requires high pressure such as some of the new generation lasers that need in excess of 22bar at the cutting head. Most piped shielding gas supplies are around 2 to 3 bar.[/I]

QUOTE]

 

[backpurge]

after a heavy welding session with long rins with the mig my regulator starts to freeze up on a large bottle, so id say its everything to do with draw off rates.

Either your flow rate is too high or the regulator is malfunctioning or not designed for youe particular use.

If you are using a liquid draw off CO2 cylinder without a heater fitted to the regulator it will freeze

 

[Luke]

It is actually a vessel within a vessel, like a huge thermos flask with a vacuum and super insulating material such as Perlite between the two vessels to reduce temperature tracking, if you get a build up of frost or ice on the actual vessel you've got big problems

Thanks for the info. Given that you can't have a perfect vacuum, and therefore a perfect insulator, what is used to keep the liquid gas that cold? Presumably the expense of keeping the gas cold is justified by the reduced running costs? Or, is the liquid allowed to manage itself, with an amount of 'boiled off' gas residing at the top of the cylinder?

Where is the liquid allowed to revert back to a gas? it doesn't look like those pipes are insulated, so is the conversion managed near the tanks, with heaters etc to stop the pipework freezing up?

I admit, my understanding of Cryogenics is pretty limited, but I'm interested to learn more.

 

[backpurge]

Luke
Please see below, it's a bit basic but hope it gives you an idea

Thanks for the info. Given that you can't have a perfect vacuum, and therefore a perfect insulator, what is used to keep the liquid gas that cold?

It is a mixture of the vessel insulation and the pressure it is stored under, you are right to say you cannot achieve an absolute vacuum but it is as near as dammit, there is very little temperature tracking from the outer to inner vessel


Presumably the expense of keeping the gas cold is justified by the reduced running costs? Or, is the liquid allowed to manage itself, with an amount of 'boiled off' gas residing at the top of the cylinder?

As you say it virtually manages itself with no running cost, dependant upon the application you can either draw off liquid from the base of the vessel or gas from the top, these things are fairly carefully calculated with regards to peoples consumption because if you do not draw off enough product the gas pressure rises in the vessel causing the safety valve to lift and vent product off to the atmosphere


Where is the liquid allowed to revert back to a gas? it doesn't look like those pipes are insulated, so is the conversion managed near the tanks, with heaters etc to stop the pipework freezing up?

The liquid starts to turn to gas as soon as it starts to leave the vessel, it usually goes through a series of vapourisers (tubes with fins on them) which aid the vapourisation process and raise the pressure with no need for any form of heating, if the application requires liquid the pipework is all super insulated and no vapourisers added

I admit, my understanding of Cryogenics is pretty limited, but I'm interested to learn more.

 

[superls]

Either your flow rate is too high or the regulator is malfunctioning or not designed for youe particular use.

If you are using a liquid draw off CO2 cylinder without a heater fitted to the regulator it will freeze

oh right, ill check my flow rate next time it happens i usually have it set around the 7-9lpm mark, how could the reg malfunction what should i check for? as far as i know its a propper argon/co2 bottle reg.

i just thought thats what happened, my big red propane cylinder does it also in certain conditions, also when refilling re-fillable lighters the fuel gets cold and starts to freeze.